Biaxially-oriented polyester film for fabrication

ABSTRACT

Biaxially-drawn polyester film for fabrication which is characterized in that it is a film comprising polyester in which ethylene terephthalate units and/or ethylene naphthalate units are the chief structural component and containing 0.1-2 wt % of a carnauba wax and 1 to 200 ppm of germanium, and the melting point of said film is 180-270° C., the angle of contact to water is 70°-120°, and the planar orientation coefficient is 0.08-0.15. This film shows outstanding release properties following repeated use, use after fabrication and use in an aqueous environment and, furthermore, it exhibits stable properties with little variation and, in particular, following lamination to metal sheet such as steel or aluminium, when used as the inner face of a fabricated metal can, it is outstanding in its non-stick properties to the contents, and provides a combination of heat resistance and processability.

TECHNICAL FIELD

The present invention relates to biaxially-oriented polyester film usedfor fabrication, and it relates to film which shows outstanding releaseproperties following repeated use, use after fabrication and use in anaqueous environment and, furthermore, which exhibits stable propertieswith little variation; in particular, it relates to biaxially-orientedpolyester film for fabrication which, when used as the inner face of afabricated metal can following lamination to metal sheet such as steelor aluminium, is outstanding in its non-stick properties in terms of thecontents and provides both heat resistance and processability.

BACKGROUND ART

Polyester film is used in various applications due to its outstandingproperties but, on account of the molecular structure of polyester, ithas poor release properties, and in order to confer such propertiesthere is generally used the technique of coating the surface with arelease component. However, this has disadvantages in that, with thesurface being subjected to deformation as a result of processing, theproperties deteriorate, and for reasons such as the strength of thecoating layer itself being inadequate, performance falls in the case ofrepeated use. Furthermore, there is also the problem that because ofpoor adhesive strength between the release layer and the polyesterlayer, following use in an aqueous environment or following a retort orboiling treatment, there is a marked reduction in performance. In thelatter case, there has been proposed overcoming the problem by providinga primer layer or reacting two components in the coating layer with acatalyst, etc, but not only are these methods unsuitable when used infood applications, there is also the problem of a lowering ofproductivity and it is difficult to stably satisfy the requiredproperties under diverse usage conditions as described above. Now,containers such as metal cans are very popular throughout the world andare essential to our way of life and, hitherto, for the purposes ofpreventing corrosion, it has been common to apply to the inner and outerfaces of the metal can a coating material formed by dissolving ordispersing an epoxy, phenolic or other such thermosetting resin in asolvent, so as to coat the metal surface. However, this kind ofthermosetting resin coating method requires a long time for the appliedmaterial to dry, so that productivity is reduced, and there is also theproblem that such a method is undesirable from the point of view ofenvironmental contamination due to the large amount of organic solventemployed.

As a method for resolving these properties, there is the method oflaminating a film to the metal can material, namely steel or aluminiumsheet or metal sheet obtained by subjecting such metal sheet to asurface treatment like plating. When a metal can is produced bysubjecting the film-laminated metal sheet to deep-drawing or ironing,the following properties are demanded of the film.

(1) It should be outstanding in its lamination to the metal sheet.

(2) It should be outstanding in its adhesion to the metal sheet.

(3) It should be outstanding in its processability and no defects suchas pin holes should be produced following fabrication.

(4) The polyester film should not separate away, or show cracking or pinhole generation when the metal can is subject to impact.

(5) There should be no adsorption of aroma components from the cancontents by the film, nor will the flavour of the contents be harmed bymaterials dissolved out of the film (referred to below as the tastecharacteristics).

(6) The contents will not stick to the can walls or to the can bottom,and it will be possible to remove the contents readily (below this isreferred to as the non-stick property).

Many proposals have been made hitherto in order to meet theserequirements. For example, in U.S. Pat. No. 5,240,779 and U.S. Pat. No.5,384,354, there are disclosed copolyester films of specified densityand planar orientation coefficient, or polyester films based on acombination of specified polyester components. However, these proposalsdo not altogether wholly satisfy the aforesaid diverse propertyrequirements and, in particular, in applications where non-stickproperties are further demanded along with outstanding lamination,impact resistance and heat resistance, it is difficult to simultaneouslyprovide such characteristics.

Objective of the Present Invention

The objective of the present invention lies in resolving the aforesaidproblems of the prior art and providing a biaxially-oriented polyesterfilm for fabrication which shows outstanding release propertiesfollowing repeated use, use after fabrication or use in an aqueousenvironment and, furthermore, which exhibits stable properties withlittle variation and, in particular, is outstanding in its lamination,fabrication, impact resistance and non-adsorption properties.

Disclosure of the Invention

In the present invention, in order for the contact angle to water andthe surface free energy to fall within these ranges, it is preferredthat a wax compound or silicone compound be added. The amount of waxcompound, etc, added is preferably 0.001 to 5 wt %, more preferably 0.1to 2 wt % and in particular 0.3 to 1.5 wt %. As examples of the waxcompounds which can be used here, there are the esters of aliphaticcarboxylic acid compounds and aliphatic alcohol compounds, and theamides of aliphatic carboxylic acid compounds and aliphatic aminecompounds, and preferably the wax is composed of a compound in which thetotal number of carbons is 30 to 120, and more preferably 40 to 100. Asexamples of such compounds, synthetic or natural waxes comprisingaliphatic esters like stearyl stearate, carnauba wax, candelilla wax,rice wax, pentaerythritol full ester, behenyl behenate, palmitylmyristate and stearyl triglyceride, are preferred from the point of viewof compatibility with the polyester. Moreover, as examples of siliconecompounds, there can be used those having a silicone structure in themain chain or in side chains, and compounds having a molecular weight of50 to 10,000 are preferred.

In particular, from the point of view of outstanding release propertiesfollowing repeated use, use after fabrication and use in an aqueousenvironment, and from the point of view of manifesting non-adsorptionproperties and enhancing hygiene in food packaging applications, etc,the addition of carnauba wax is preferred and especially refinedcarnauba wax. The amount of the carnauba wax compound or the like addedto the film is preferably from 0.1 to 2 wt %, more preferably 0.2 to 0.9wt % and in particular from 0.3 to 0.8 wt %.

As a result of a thorough investigation into methods for adding andincorporating carnauba wax into the polyester in the present invention,it was found that, in terms of enhancing the carnauba wax dispersionproperties and manifesting stable properties, and also in terms ofsuppressing contamination in the film production process, the followingmethods of addition in the polymerization process are preferred:—

(1) The method of adding the carnauba wax at the time of the polyesterpolymerization, and

(2) The method of producing, by polymerization, a master batch (acarnauba wax master polyester) to which a large quantity of carnauba waxis added, and then mixing this with a specified amount of polyestercontaining no, or just a small amount of, carnauba wax (the diluentpolyester) and kneading.

In the present invention, in the case of polyester where carnauba wax isadded, carrying out the polymerization using a germanium catalyst isespecially preferred from the point of view of enhancing the dispersionproperties, and it is preferred that the germanium element content befrom 1 to 200 ppm, more preferably 10 to 100 ppm and in particular 20 to80 ppm. Again, in the case of obtaining film by method (2), it ispreferred that there be used germanium catalyst as described above forthe carnauba wax master polymer but the diluent polymer is notrestricted to one employing germanium catalyst. Consequently, dependingon the preparation method for adding wax to the polymer, and dependingon whether there is used a master batch or again on whether the film hasa composite structure, the germanium element content in the film ispreferably 0.1 to 200 ppm, more preferably 1 to 200 ppm, still morepreferably 10 to 100 ppm and in particular 20 to 80 ppm.

The biaxially-oriented polyester film for fabrication of the presentinvention which meets such objectives is a biaxially-oriented polyesterfilm for fabrication characterized in that it is a film comprisingpolyester in which ethylene terephthalate units and/or ethylenenaphthalate units are the chief structural component, and the meltingpoint of said film is 180-270° C., the angle of contact to water is70°-120°, and the planar orientation coefficient is 0.08-0.15.

Furthermore, preferred embodiments of the biaxially-oriented polyesterfilm for fabrication of the present invention are those where thesurface free energy is 20-40 mN/m, where there is contained 0.1 to 2 wt% of wax compound and/or silicone compound, where there are 0.2 to 5 wt% of inorganic particles and/or organic particles present in the film,where the carnauba wax content is 0.1 to 2 wt % and the germaniumelement content is 1 to 200 ppm, where production is carried out bydilution of a master batch containing 1 to 200 ppm of germanium elementand 1 to 10 wt % of carnauba wax, and where it is a composite filmcomprising a structure with two or more layers at least one face ofwhich consists of the aforesaid polyester film, and thisbiaxially-oriented polyester film for fabrication is ideally used inpackaging applications and laminating to metal sheet.

Best Mode for Carrying out the Invention

The biaxially-oriented polyester film for fabrication of the presentinvention is a polyester wherein ethylene terephthalate units and/orethylene naphthalate units are the chief structural component.

In the present invention, this polyester wherein ethylene terephthalateunits and/or ethylene naphthalate units are the chief structuralcomponent is a polyester in which the ethylene terephthalate unitsand/or ethylene naphthalate units constitute at least 70 mol % and, fromthe point of view of heat resistance and impact resistance, preferablyat least 85 mol % and more preferably at least 95 mol %.

There may be copolymerized other dicarboxylic acid and/or glycolcomponents, and as the dicarboxylic acid component there can be used forexample an aromatic carboxylic acid such as isophthalic acid,naphthalenedicarboxylic acid, diphenyldicarboxylic acid,diphenylsulphone dicarboxylic acid, diphenoxyethanedicarboxylic acid,5-sodiumsulpho-isophthalic acid or phthalic acid, an aliphaticdicarboxylic acid such as oxalic acid, succinic acid, adipic acid,sebacic acid, dimer acid, maleic acid or fumaric acid, an alicyclicdicarboxylic acid such as cyclohexane dicarboxylic acid, or ahydroxycarboxylic acid such as p-hydroxybenzoic acid. Furthermore, asthe glycol component, there can be used for example an aliphatic glycolsuch as propanediol, butanediol, pentanediol, hexanediol or neopentylglycol, an alicyclic glycol such as cyclohexanedimethanol, an aromaticglycol such as bisphenol A or bisphenol S, or diethylene glycol. Theremay also be used two or more types of such dicarboxylic acid or glycolcomponents.

Furthermore, insofar as the effects of the present invention are notimpaired, it is also possible to copolymerize a polyfunctional compoundsuch as trimellitic acid, trimesic acid or trimethylolpropane in thepolyester or copolyester used in the present invention.

In the present invention, components which are preferably copolymerizedare, for example, butanediol, diethylene glycol, polyethylene glycol,cyclohexanedimethanol, sebacic acid, adipic acid, dimer acid,isophthalic acid and naphthalenedicarboxylic acid.

From the point of view of the heat resistance and the fabricationproperties, it is necessary in the present invention that the meltingpoint of the film lies in the range 180 to 270° C. Furthermore, in termsof preventing change with passage of time following fabrication, themelting point of the film is preferably 246-265° C. and more preferably250-260° C.

In the present invention, from the point of view of the lamination,fabrication and impact resistance properties, it is necessary that theplanar orientation coefficient (f_(n)) of the biaxially-oriented filmlies in the range 0.08 to 0.15. If the planar orientation coefficientlies below this range, the impact resistance is impaired, while if itlies above this range then the lamination and fabrication properties areimpaired. From the point of view of the impact resistance andfabrication properties, it is particularly preferred that the planarorientation coefficient lies in the range 0.120 to 0.145.

From the point of view of the lamination and fabrication properties, thedifference between the film lengthwise direction refractive index(n_(x)) and the widthwise direction refractive index (n_(y)) of thebiaxially-oriented polyester film for fabrication of the presentinvention (the birefringence: Δn=n_(x)−n_(y)) preferably lies in therange −0.001 to −0.050, and more preferably Δn lies in the range −0.005to −0.02.

Moreover, in the present invention, from the point of view of the mouldrelease and non-stick properties, it is necessary that the contact anglein terms of water be from 70° C. to 120°, more preferably from 75° to110°, still more preferably from 80° to 100° and in particular from 85°to 100°. If the contact angle with water exceeds 120°, the film is tooslippery and its winding and processing properties may be impaired, andthe nip in lamination or the support in fabrication may be unstable.

Furthermore, in the present invention, it is preferred from the point ofview of further enhancing the release and non-stick properties that thesurface free energy be 20-40 mM/m, and more preferably 22-38 mN/m, 25-35mN/m.

The film structure of the biaxially-oriented polyester film forfabrication of the present invention may of course be a monolayer, butit may also be a laminate structure of two layers A/B, three layersA/B/A or A/B/C, or more than three layers, and the laminate thicknessratio may be freely set, but two layers A/B are preferred.

Here, the A layer, which is that not facing the steel sheet, is thelayer which is to display non-stick properties. Using lamination so thatan aforesaid wax compound or silicone compound is added to the A layerwhich is to display the non-stick properties, or coating just the Alayer side, is preferred from the point of view of suppressing offset tothe non-stick face and enhancing processability and productivity.

In the present invention, from the point of view of the heat resistanceand the impact resistance following processing, it is necessary that thepolyester in which ethylene terephthalate units and/or ethylenenaphthalate units are the chief structural component bebiaxially-oriented. The biaxial orientation method may be by inflationdrawing, simultaneous biaxial drawing or sequential biaxial drawing butsimultaneous biaxial drawing or sequential biaxial drawing arepreferred.

Furthermore, in the present invention, from the point of view ofprocessability, it is preferred that the average breaking elongation at100° C. in the lengthwise and widthwise directions be 200-500% and morepreferably 250-450%.

Moreover, in terms of uniformity of impact resistance and processabilityin each direction, it is preferred that the absolute value of thedifference between the lengthwise direction breaking elongation and thewidthwise direction breaking elongation at 100° C. be no more than 50%,with no more than 50%, with no more than 40% being particularlypreferred. Furthermore, clockwise from the lengthwise direction, theaverage of the breaking elongation in the direction at 45° and thebreaking elongation in the direction at 135°, is preferably 200-500% andmore preferably 250-450%, at 100° C. In addition, the absolute value ofthe difference between the lengthwise direction breaking elongation andthe breaking elongation in the direction 45° clockwise from thelengthwise direction, at 100° C., is preferably no more than 50% and inparticular no more than 40%. Here, the breaking elongation is the valuemeasured using a Tensilon (tensile testing machine) at an extension rateof 500 mm/min, in an atmosphere at 100° C. and 65% RH, for a sample oflength 50 mm and width 10 mm.

In the present invention, from the point of view of processability andheat resistance, the intrinsic viscosity of the polyester is preferably0.4 to 1.5 dl/g, more preferably 0.5 to 1.3 dl/g and, in particular, 0.6to 1.2.

In the present invention, a film density of from 1.35 to 1.41 g/cm³ ispreferred in terms of good processability, with the range 1.36 to 1.4g/cm³ being particularly preferred. If the density is too low, thefabrication properties are impaired due to wrinkles, etc, while if thedensity is too high unevenness in the processability is produced.

When producing the polyester from which the biaxially-oriented polyesterfilm for fabrication of the present invention is composed, it ispossible to use a reaction catalyst. Examples of the reaction catalystare alkali metal compounds, alkaline earth metal compounds, zinccompounds, lead compounds, manganese compounds, cobalt compounds,aluminium compounds, antimony compounds and titanium compounds, and asdiscoloration preventing agents there can be used phosphorus compoundsfor example. Preferably, normally at any stage prior to the completionof the polyester production, an antimony compound, a germanium compoundor a titanium compound is added as polymerization catalyst.

As examples of such methods, taking the particular case of a germaniumcompound there is the method of adding a germanium compound powder as itis, or the method of adding a germanium compound dissolved in the glycolcomponent which comprises the polyester starting material as describedin JP-B-54-22234. Examples of the germanium compounds include germaniumdioxide, germanium hydroxide containing water of crystallization,germanium alkoxides such as germanium tetramethoxide, germaniumtetraethoxide, germanium tetrabutoxide and germanium ethyleneglycoxide,germanium phenoxide compounds such as germanium phenolate and germaniumβ-naphtholate, phosphorus-containing germanium compounds such asgermanium phosphate and germanium phosphite, germanium acetate and thelike. Of these, germanium dioxide is preferred. As antimony compounds,there can be used for example an antimony oxide such as antimonytrioxide, or antimony acetate. As titanium compounds, there can befavourably employed alkyl titanate compounds such as tetraethyl titanateand tetrabutyl titanate.

Next, there is explained the case of the addition of germanium dioxideas the germanium compound when producing polyethylene terephthalate. Theterephthalic acid component and the ethylene glycol are made to undergoester-interchange or esterification, the germanium dioxide andphosphorus compound then added after which, under high temperature andreduced pressure, the polycondensation reaction is conducted until thereis a specified diethylene glycol content, and polymer containing theelement germanium is thereby obtained. Furthermore, preferably thepolymer obtained is subjected to a solid phase polymerization at atemperature below the melting point under reduced pressure or in aninert atmosphere, so that the acetaldehyde content is reduced, and aspecified intrinsic viscosity and carboxyl end-groups are obtained.

In the present invention, from the point of view of enhancing thecompatibility with wax, the carboxyl end-group content of the polyesteris preferably 30-55 eq/ton (equivalents per ton), more preferably 35-50eq/ton and in particular 40-48 eq/ton.

Again, it is desirable from the point of view of hygiene properties, andalso in terms of the maintenance of good hygiene properties with passageof time or when subject to a thermal history as a result of processing,that the polyester in the present invention has a diethylene glycolcomponent content preferably in the range 0.01 to 4 wt %, morepreferably in the range 0.01 to 3 wt % and in particular in the range0.01 to 2 wt %. Furthermore, there may be added from 0.0001 to 1 wt % ofantioxidant. Moreover, diethylene glycol may also be added at the timeof polymer production within a range such that the properties are notimpaired.

In addition, it is desirable in terms of ensuring good hygieneproperties that the acetaldehyde content of the film preferably be nomore than 30 ppm, more preferably no more than 25 ppm and in particularno more than 20 ppm. With regard to the method for keeping theacetaldehyde content of the film no more than 30 ppm, there is themethod of eliminating the acetaldehyde produced by thermal decompositionat the time of the polyester production in the polycondensationreaction, etc, by heat-treating the polyester under reduced pressure orin an inert gas atmosphere at a temperature below the melting point ofthe polyester, preferably the method of subjecting the polyester tosolid phase polymerization under reduced pressure or in an inert gasatmosphere at a temperature of at least 150° C. but less than themelting point, or the method of melt extrusion using a vacuum ventedextruder, or again the method whereby when melt-extruding polymer theextrusion is carried out over a short time, preferably for an averageresidence time of no more than 1 hour, within the range melting point+30° C. and preferably melting point +25° C., for the highest meltingpolymer present.

As an example of the method of producing the biaxially-orientedpolyester film for fabrication in the present invention, each polyesteris optionally dried, after which it is supplied to a known melt extruderand extruded in the form of sheet from a slit-shaped die, then made toclosely adhere to a casting drum by a system such as electrostaticpinning, so that it is cooled and solidified and an undrawn sheetobtained. The drawing system may be either a simultaneous or sequentialbiaxial drawing system, and by subjecting this undrawn sheet to drawingand heat treatment in the film lengthwise and widthwise directions, filmis obtained of the desired planar degree of orientation. From the pointof view of the film quality, it is preferred that it be based on astenter system, and either a sequential biaxial drawing system, in whichdrawing is carried out in the lengthwise direction after which drawingis conducted in the widthwise direction, or a simultaneous biaxialdrawing system, in which the lengthwise direction and widthwisedirection drawing are performed essentially simultaneously, isdesirable. The draw ratio in each direction will be in the range from1.5 to 4.0, preferably 1.8 to 4.0. Either the lengthwise or thewidthwise draw ratio can be greater than the other, or they may both bethe same.

The elongation rate is desirably in the range 1000% per minute to200,000% per minute, and the drawing temperature can be any temperatureproviding that it is above the glass transition temperature of thepolyester and less than the glass transition temperature +80° C., butnormally 80-150° C. is preferred.

Furthermore, following the biaxial drawing, the film is subjected to aheat treatment and this heat treatment can be carried out by any knownmethod, for example in an oven or on a heated roller. The heat treatmenttemperature can usually be any temperature above 120° C. and below 245°C. but, preferably, it is 120-240° C. Again, any heat treatment time canbe employed but, normally, it is preferred that the heat treatment beconducted for from 1 to 60 seconds. The heat treatment may also becarried out while allowing the film to relax in its lengthwise directionand/or in its widthwise direction. Moreover, redrawing may be carriedout one or more times in each direction, after which heat treatment mayalso be carried out.

Again, in order to enhance the non-stick property, the handling and theprocessability of the biaxially-oriented polyester film for fabricationof the present invention, it is necessary to employ internal particles,inorganic particles or organic particles in the film. The amount thereofadded is from 0.005 to 10 wt %, but in particular it is preferred thatthere be from 0.2 to 5 wt %, and more preferably 0.3 to 4 wt %, of theinorganic particles and/or organic particles present in the film. Ofsuch particles, the use of so-called external particles such asinorganic particles and/or organic particles of average particlediameter 0.01 to 10 μm is preferred. In particular, it is preferred thatinorganic particles and/or organic particles of average particlediameter 0.1 to 5 μm be added to the film used at the inner face of acan. As examples of methods for depositing internal particles, there arethe techniques described in JP-A-48-61556, JP-A-51-12860, JP-A-53-41355and JP-A-54-90397. Furthermore, there may be employed the joint usethereof with other particles as in JP-A-55-20496 and JP-A-59-204617.

If particles of average particle diameter exceeding 10 μm are used, filmdefects tend to be produced so this is undesirable. Examples of theinorganic particles and/or organic particles are inorganic particlessuch as wet-based or dry-based silica, colloidal silica, aluminiumsilicate, titanium oxide, calcium carbonate, calcium phosphate, bariumsulphate, alumina, mica, kaolin and clay, and organic particles with astructural component comprising styrene, silicone, acrylic acid or thelike. Of these, there can be cited inorganic particles such as wet-basedand dry-based colloidal silica and alumina, and organic particles with astructural component comprising styrene, silicone, acrylic acid,methacrylic acid, polyester, divinyl benzene and the like. Two or moretypes of such internal particles, inorganic particles and/or organicparticles can be jointly employed.

Furthermore, from the point of view of adhesion, the centre line averageroughness Ra is preferably in the range 0.005 to 0.1 μm, more preferably0.008 to 0.05 μm. Moreover, high speed processability is enhanced if theratio in terms of the maximum roughness Rt, that is to say the ratioRt/Ra, is 1 to 100, and preferably 5 to 50.

Again, in the case where adhesive strength is required at one face, theadhesion properties can be enhanced by carrying out a surface treatmentsuch as a corona discharge treatment and the corona discharge treatmentintensity at this time is preferably 5 to 50 W·min/m², more preferably10 to 45 W·min/m².

Additives such as antistatic agents, heat stabilizers, antioxidants,nucleating agents, weathering agents and ultraviolet absorbers can alsobe employed in the biaxially-oriented polyester film for fabrication ofthe present invention, in an amount such that the objectives of thepresent invention are not impaired. Again surface texturizing such asembossing or sand matting, or surface treatments such as a plasmatreatment or alkali treatment, can also be carried out where required.Moreover, the film of the present invention can also be coated orprinted with treatment agents for facilitating adhesion, or withantistatic agents, moisture- or gas-barrier agents (polyvinylidenechloride or the like), tacky adhesives, adhesives, flame retardants,ultraviolet absorbers, matting agents, pigments, dyes or the like, and,for the purposes of providing light screening properties, moisture/gasbarrier properties, surface electro-conductivity, infrared reflectiveproperties or the like, there may be carried out the vacuum depositionof a metal or metal compound such as aluminium, aluminium oxide, siliconoxide, palladium or the like. The objectives thereof and the methodsemployed are not to be restricted to those mentioned.

The biaxially-oriented polyester film for fabrication of the presentinvention can be favourably employed for fabrication processes, forexample it is ideal for container applications by lamination to metalsheet, paper or the like, and then processing. In particular, it can befavourably used as film for laminating to metal sheet and fabricating,in order to preserve foods containing proteins (for example meat oregg).

Below, practical examples of the present invention are described butthese examples are not to restrict the interpretation of the inventionin any way.

Measurements and evaluations of the properties were carried out by thefollowing methods.

(1) Melting Point (Tm)

The melting point was measured using a differential scanning calorimeterDSC2 (made by Perkin Elmer). 10 mg of sample was melted and held for 5minutes at 280° C. under a current of nitrogen, and then rapidly cooledusing liquid nitrogen. The sample obtained was heated at a rate of 10°C./minute and the endotherm peak temperature due to crystal melting wastaken as the melting point (Tm).

(2) Carboxyl End-group Content

This was determined by dissolving film at 95° C. in o-cresol/chloroform(weight ratio 7/3) and carrying out potentiometry with alkali.

(3) Intrinsic Viscosity

This was measured at 25° C. after dissolving the polyester ino-chlorophenol

(4) Film Elongation-I

The film elongation was measured at 100° C. in accordance withASTM-D-882-81 (method A), and the processability assessed as follows.Both grades A and B are satisfactory.

Grade A: average breaking elongation in the lengthwise and widthwisedirections =300-500%.

Grade B: average breaking elongation in the lengthwise and widthwisedirections =200-300%.

Grade C: average breaking elongation in the lengthwise and widthwisedirections =0-200%.

(5) Film Elongation-II

The film elongation was measured at 100° C. in accordance withASTM-D-882-81 (method A), and the processability assessed as follows.Both grades A and B are satisfactory. This is an index of impactresistance.

Grade A: difference in average breaking elongation in the lengthwise andwidthwise directions is 0-50%.

Grade B: difference in average breaking elongation in the lengthwise andwidthwise directions is 50-100%.

Grade C: difference in average breaking elongation in the lengthwise andwidthwise directions is over 100%.

(6) Film Elongation-III

The film elongation was measured at 100° C. in accordance withASTM-D-882-81 (method A), and the processability assessed as follows.Both grades A and B are satisfactory.

Grade A: clockwise from the lengthwise direction, the average breakingelongation in the direction at 45° and breaking elongation in thedirection at 135°=300-500%.

Grade B: clockwise from the lengthwise direction, the average breakingelongation in the direction at 45° and breaking elongation in thedirection at 135°=200-300%

Grade C: clockwise from the lengthwise direction, the average breakingelongation in the direction at 45° and breaking elongation in thedirection at 135°=0-200%.

(7) Contact Angle to Water

By the known method and using water as the measurement liquid, thestatic contact angle of water to the film surface was determinedemploying a contact angle meter (model CA-D made by Kyowa Kaimen KagakuK.K.).

(8) Surface Free Energy

By the known method, and using three types of measurement liquid, namelywater, ethylene glycol and formamide, the static contact angle of eachof these liquids to the film surface was determined employing a contactangle meter (model CA-D made by Kyowa Kaimen Kagaku K.K.). 10measurements were made for each liquid, then the average contact angle(θ) and the surface tension of the measurement liquid (j) for eachcomponent were respectively introduced into the following formula, andthe simultaneous equations comprising the three equations solved forγ^(L), γ⁺ and γ⁻.${\left( {\gamma^{L}\gamma_{j}^{L}} \right)^{\frac{1}{2}} + {2\left( {\gamma^{+}\gamma_{j}^{-}} \right)^{\frac{1}{2}}} + {2\left( {\gamma_{j}^{+}\gamma^{-}} \right)^{\frac{1}{2}}}} = {\frac{\left( {1 + {\cos \quad \theta}} \right)}{2}\left\lbrack {\gamma_{j}^{L} + {2\left( {\gamma^{+}\gamma^{-}} \right)^{\frac{1}{2}}}} \right\rbrack}$$\gamma = {\gamma^{L} + {2\left( {\gamma^{+}\gamma^{-}} \right)^{\frac{1}{2}}}}$$\gamma_{j} = {\gamma_{j}^{L} + {2\left( {\gamma_{j}^{+}\gamma_{j}^{-}} \right)^{\frac{1}{2}}}}$

Here, γ, γ^(L), γ⁺ and γ⁻ respectively denote the surface free energy,the long distance forces term, the Lewis acid parameter and the Lewisbase parameter for the film surface.

Furthermore, γ_(j), γ_(j) ^(L), γ_(j) ⁺ and γ_(j) ⁻ respectively denotethe surface free energy, the long distance forces term, the Lewis acidparameter and the Lewis base parameter for the measurement liquid used.

For the surface tensions of the liquids used here, there were used thevalues proposed by Oss (“fundamentals of Adhesion”, L. H. Lee (Ed),p153, Plenum ess, New York (1991).)

9) Planar Orientation Coefficient

The planar orientation coefficient was measured using an Abberefractometer with the sodium D line (wavelength 589 nm) as the lightsource. From the refractive indexes (N_(x), N_(y), N_(z)) in thelengthwise, widthwise and thickness directions, the planar orientationcoefficient f_(n) was determined from the relationf_(n)=(N_(x)+N_(y))/2−N_(z).

(10) Processability

After laminating at 70 m/min to a TFS steel sheet (thickness 0.2 mm)heated to 30° C. above the film melting point, rapid cooling was carriedout with a water bath at 50° C. The laminated steel sheet was fabricatedat a reduction factor of 20% and the processability assessed accordingto the appearance of the can obtained as follows.

Grade A: film did not show whitening, splitting or wrinkling.

Grade B: some wrinkling or slight whitening of the film seen but nosplitting.

Grade C: whitening, splitting and wrinkling of the film seen.

(11) Non-stick Property

The non-stick property was evaluated by eye based on the followinggrades by ⅔ filling the can obtained with contents comprising a 3:2:1mixture of egg, meat and flour, and then subjecting the can to a retorttreatment for 30 minutes at 125° C., after which it was removed and thestate of adhesion to the can walls assessed.

Grade AA: absolutely no adhesion.

Grade A: essentially no adhesion.

Grade B: slight remaining adhering material.

Grade C: adhering material over about ¼ entire can.

Grade D: adhering material over about ½ entire can.

Grade E: adhering material remaining over entire can.

(12) Release Property

20×50 mm cellophane tape was affixed to the film and then peeled away,after which the surface free energy S_(f2) was measured, and thenevaluation was performed as follows based on the difference ΔS_(f)(mN/m) between this and the original surface free energy S_(f1).

Grade A: 0-1

Grade B: 1-2

Grade C: 2-3

Grade D: 3-5

Grade E: over 5

EXAMPLE 1

As the polyester, chip A of polyethylene terephthalate (antimonytrioxide catalyst, intrinsic viscosity 0.65, diethylene glycol 2.8 mol%) to which 0.8 wt % stearyl stearate wax compound had been added, wasproduced by heat treating an ethylene glycol slurry containingflocculated silica particles for 2 hours at 190° C. and adding theslurry to the esterification product between terephthalic acid andethylene glycol, and then carrying out the polycondensation reaction.After measuring out a specific quantity of this chip, it was dried undervacuum for 3 hours at 180° C. and supplied to a single screw extruder,then discharged from a normal die and cooled and solidified on amirror-surface cooled drum while performing electropinning (7 kv) andthere was obtained undrawn film containing 0.8 wt % of stearyl stearatetype wax compound (drum rotation rate 40 m/min). This undrawn film wasdrawn by a factor of 2.8 in the lengthwise direction at a temperature of105° C. and then cooled to 40° C., after which it was pre-heated for 5seconds at a temperature of 115° C. and then drawn by a factor of 2.8 inthe widthwise direction at the same temperature, following which it wasgiven a 5 second 5% relaxation heat treatment at 180° C., and there wasobtained the biaxially-oriented polyester film of thickness 16 μm shownin Table 2. As shown in Table 2, it was confirmed that good propertieswere exhibited.

EXAMPLES 2 and 3

From extruder I (layer A) and extruder II (layer B), and using thepolyesters shown in Table 1, laminated biaxially-oriented polyester filmof properties as shown in Table 2 was obtained by melting each polyesterand superimposing these just in front of the die, and by varying thedrawing conditions in Example 1. As shown in Table 2, it was confirmedthat outstanding properties were exhibited.

EXAMPLES 4 and 5

Biaxially-drawn polyester film was obtained by varying the polymercompositions and the thicknesses in accordance with Tables 1 and 2. Asshown in Table 2, it was confirmed that good properties were exhibited.

EXAMPLE 6

After measuring out specified quantities of polyester (1) and (2) chipin accordance with Tables 1 and 2, these were dried under vacuum for 3hours at 180° C. and supplied to extruder I (A layer) and extruder II (Blayer), and after discharge from an ordinary die, cooling andsolidification were carried out on a mirror-surface cooling drum whileperforming electropinning (7 kv), and undrawn film obtained. Thisundrawn film was subjected to simultaneous biaxial drawing at atemperature of 105° C. by a factor of 3.4 in the lengthwise directionand by a factor of 3.2 in the widthwise direction, following which thefilm was given a 5 second 5% relaxation heat treatment at 210° C., andthere was obtained the biaxially-oriented polyester film of thickness 15μm shown in Table 1. As shown in Table 2, it was confirmed thatoutstanding properties were exhibited.

EXAMPLES 7 to 9

Biaxially-oriented polyester films were obtained in the same way as inExample 6 by varying the polymer compositions and the drawing conditionsin accordance with Table 3. As shown in Table 4, it was confirmed thatoutstanding properties were exhibited. However, in the case of Example9, since the melting point was lowered, there was a slight reduction inthe heat resistance.

COMPARATIVE EXAMPLES 1 to 3

Films were obtained by carrying out film production in the same way asin Example 1 with the types of polyester and the additives changed tothose shown in Table 3. It is clear from Table 4 that the films fromComparative Examples 1 to 3 were inferior in their properties.

In the tables, the codes used had the following meanings.

PET: polyethylene terephthalate.

PET/I: polyethylene terephthalate with copolymerized isophthalic acid.

PET/S: polyethylene terephthalate with copolymerized sebacic acid.

PET/S: polyethylene terephthalate with copolymerized naphthalenedicarboxylic acid.

TABLE 1 Example Number 1 2 3 4 5 6 Polymer (1) Composition PET PET PETPET PET/N PET (5 mol) Polymerization Catalyst Type Sb₂O₃ GeO₂ Sb₂O₃Sb₂O₃ Sb₂O₃ Sb₂O₃ Conc. (ppm) Sb:200 Ge:45 Sb:100 Sb:150 Sb:300 Sb:180Particles Type flocculated spherical flocculated flocculated flocculatedflocculated silica silica silica silica silica silica Av. particle 0.60.4 1.5 1.5 2.5 1.4 size (μm) Conc. (%) 0.04 0.3 0.15 0.2 0.14 0.1Particles Type flocculated spherical aluminium silica silica silicateAv. particle 1.2 2.5 0.2 size (μm) Conc. (%) 0.06 0.15 0.5 Additive Typestearyl carnauba silicone calcium carnauba stearate wax compoundstearate wax Conc. (%) 0.8 0.5 0.4 0.5 0.5 Polymer (2) Composition PETPET/I PET (5 mol) Polymerization Catalyst Type GeO₂ Conc. (%) Ge:40Particles Type spherical flocculated silica silica Av. particle 1.4 1.5size (μm) Conc. (%) 0.08 0.1 Additive Type carnauba wax Conc. (%) 2.0

TABLE 2 Example Number 1 2 3 4 5 6 A-layer Polymer (1)/Polymer (2) 10/010/0 10/0 10/0 10/0 5/5 Polyester PET PET PET PET PET/N PET (5 mol)Melting Point (° C.) 254 254 254 254 247 254 Particles Type flocculatedspherical flocculated flocculated flocculated flocculated silica silicasilica silica silica silica Av. 0.6 0.4 1.5 1.5 2.5 1.5 particle size(μm) Conc. (%) 0.04 0.3 0.15 0.2 0.14 0.05 Particles Type flocculatedspherical aluminium silica silica silicate Av. 1.2 2.5 0.2 particle size(μm) Conc. (%) 0.06 0.15 0.5 Additives Type stearyl carnauba siliconecalcium carnauba carnauba stearate wax compound stearate wax wax Conc.(%) 0.8 0.5 0.4 0.5 0.5 1.0 Ge concentration (%) 0 45 0 0 0 10 Thickness16 2 2 16 18 3 B-layer Polymer(1)/Polymer(2) 0/10 0/10 10/0 PolyesterPET PET/I PET (5 mol) Melting Point (° C.) 254 247 254 Particles Typespherical flocculated flocculated silica silica silica Av. 1.4 1.5 1.4particle size (μm) Conc. (%) 0.08 0.1 0.1 Additives Type Conc. (%) Geconcentration (ppm) 45 0 0 Thickness 14 14 12 Ge Concentration in Film(ppm) 0 45 0 0 0 2 Contact Angle to Water (°) 82 89 83 73 88 92 SurfaceFree Energy 38 36 39.5 42 37 33 Carboxyl End Group Content (eq/ton) 3839 35 32 34 43 Intrinsic Viscosity (dl/g) 0.63 0.64 0.65 0.66 0.64 0.6Face Laminated to Metal Sheet B layer B layer Elastic Modulus (GPa) 2.73.2 3.0 3.4 2.7 3.3 Elongation (%) Elongation I A B A B A B ElongationII A A B A A B Elongation III A B A B A B Planar Orientation Coefficient0.125 0.147 0.135 0.145 0.119 0.15 Δn −0.007 −0.002 −0.015 +0.005 −0.012−0.008 Processability A B A B A B Release Property B A C B B A Non-StickProperty A AA B A A AA

TABLE 3 Example Numbers Comparative Example Numbers 7 8 9 1 2 3 Polymer(1) Composition PET PET PET/l PET PET/S PEN (6 mol) PolymerizationCatalyst Type Sb₂O₃ Sb₂O₃ GeO₂ Sb₂O₃ Sb₂O₃ Sb₂O₃ Conc. (ppm) Sb:200Sb:150 Ge:45 Sb:150 Sb:150 Sb:350 Particles Type spherical flocculatedspherical flocculated spherical flocculated silica silica silica silicasilica silica Av. particle 0.9 0.8 1.2 1.4 0.2 0.2 size (μm) Conc. (%)0.08 0.12 0.08 0.05 0.08 0.07 Particles Type Av. particle size (μm)Conc. (%) Additive Type Conc. (%) Polymer (2) Composition PET PET PET/I(5 mol) Polymerization Catalyst Type GeO₂ GeO₂ GeO₂ Conc. (%) Ge:50Ge:50 Ge:45 Additive Type carnauba carnauba carnauba wax wax wax Conc.(%) 0.7 1 0.5

TABLE 4 Example Number Comparative Example Number 7 8 9 1 2 3 A-layerPolymer (1)/Polymer (2) 0/10 7/3 0/10 10/0 10/0 10/0 Polyester PET PETPET/l PET PET/S PEN Melting Point (° C.) 254 254 242 254 222 265Particles Type flocculated flocculated spherical flocculated silicasilica silica silica Av. 0.8 1.4 0.2 0.2 particle size (μm) Conc. (%)0.84 0.05 0.08 0.07 Additives Type carnauba carnauba carnauba wax waxwax Conc. (%) 0.7 0.3 0.5 Ge concentration (%) 50 15 45 0 0 Thickness 515 1 16 15 B-layer Polymer(1)/Polymer(2) 10/0 10/0 Polyester PET PET/IMelting Point (° C.) 254 242 Particles Type spherical spherical silicasilica Av. 0.9 0.8 particle size (μm) Conc. (%) 0.08 0.08 Additive TypeConc. (%) Ge concentration (ppm) 0 45 Thickness 10 14 Ge Concentrationin Film (ppm) 17 15 45 0 0 0 Contact Angle to Water (°) 90 85 89 67 6465 Surface Free Energy 34 38 38 45 46 46 Carboxyl End Group Content(eq/ton) 40 34 29 22 35 28 Intrinsic Viscosity (dl/g) 0.6 0.6 0.58 0.750.57 0.62 Face Laminated to Metal Sheet B layer B layer Elastic Modulus(GPa) 2.9 3.6 3.1 4.1 2.4 4.9 Elongation (%) Elongation I A B A C B CElongation II A B A C B C Elongation III A B A C B C Planar OrientationCoefficient 0.145 0.15 0.134 0.168 0.078 0.17 Δn −0.01 +0.003 −0.015−0.025 −0.015 −0.025 Processability B B A C B C Release Property A B B EE E Non-Stick Property A B B E E E

What is claimed is:
 1. Biaxially-oriented polyester film for fabricationwhich is characterized in that it is a film comprising polyester inwhich ethylene terephthalate units and/or ethylene naphthalate units arethe chief structural component and containing 0.1-2 wt % of a carnaubawax and 1 to 200 ppm of germanium, and the melting point of said film is180-270° C., the angle of contact to water is 70°-120°, and the planarorientation coefficient is 0.08-0.15.
 2. Biaxially-oriented polyesterfilm for fabrication according to claim 1 where the surface free energyis 20-40 mN/m.
 3. Biaxially-oriented polyester film for fabricationaccording to claim 1 which is characterized in that 0.2-5 wt % ofinorganic particles and/or organic particles are included in the film.4. Biaxially-oriented polyester film for fabrication which ischaracterized in that it is a laminate film comprising a structure of atleast two layers, and at least one face is polyester film according toclaim
 1. 5. Biaxially-oriented polyester film for fabrication accordingto claim 1 which is characterized in that it is used in food packagingapplications.
 6. Biaxially-oriented polyester film for fabricationaccording to claim 1 which is characterized in that it is used bylamination to metal sheet.
 7. A method of producing thebiaxially-oriented polyester film for fabrication according to claim 1which is characterized in that production is carried out by dilution ofa master batch containing 1-200 ppm of germanium element and 1-10 wt %of carnauba wax.
 8. Biaxially-oriented polyester film for fabricationaccording to claim 1 which is characterized in that the average of thelengthwise and widthwise breaking elongation at 100° C. is 200 to 500%.9. Biaxially-oriented polyester film for fabrication according to claim1 which is characterized in that the absolute value of the differencebetween the lengthwise breaking elongation and the widthwise breakingelongation at 100° C. is no more than 50%.
 10. Biaxially-orientedpolyester film for fabrication according to claim 1 where the meltingpoint of the film is 246-265° C.